Avocado fruits are widely consumed as food throughout the world, and are also diversely used for medicinal and cosmetic purposes. Various preparations containing freshly mashed avocado as well as avocado oil are recommended to be applied onto the skin to revitalize and to improve its appearance.
Many studies have been conducted regarding non-saponifiable fractions of avocado oil. The unsaponified material (non-saponifiable fraction) is the fraction of fatty material that is insoluble in water and may be extracted with an organic solvent after a prolonged alkaline hydrolysis. Oil saponification is used for isolating free fatty acids from triglycerides that compose more than 90% of plant-origin oil. To a certain extent, unsaponifiables are the byproducts of soap technology although the presence of some unique phytochemicals makes unsaponifiables useful ingredients for cosmetic and pharmaceutical applications in their own right. The content of non-saponifiables in avocado oil ranges from 2% to 7%, and they are a very attractive fraction of avocado extracts for cosmetic and therapeutic applications, due to the biological activity of their constituencies.
Polyhydroxylated fatty alcohols (PFA) are unique crystalline lipid molecules that may be found in avocado extracts. PFA lipids all have a long aliphatic (mostly C17) chain with one end unsaturated with a double or triple (acetylenic) bond, and the other end having three hydroxyl groups. Naturally, one of the hydroxyl groups in position 1 or 4 of most PFAs are acetylated, as shown in structures A, B, D, E In FIG. 1. Studies of biological activity of PFA demonstrated antifungal [Dominguez, F et al., 2005, Phytochemistry 54, 183-189], antibacterial [Neeman, I. et al., 1970, Appl. Microbiol. 19, 470-473] and anti-parasitic properties [Abe, F., et al., 2005. Biol. Pharm. Bull. 28, 1314-1317] and show to inhibit acetyl CoA carboxylase activity [Hashimura H, et al., (2001) Biosci Biotechnol Biochem 65:1656-1658].
A recent study demonstrated the photo protective and anti-inflammatory potential of PFAs at the molecular level [Rosenblat G et al., Arch Dermatol Res. 2011 May; 303(4):239-46].
In separate experiments, it was demonstrated that polyhydroxylated fatty alcohols attenuate experimental dermatitis and may be used topically in pharmaceutical applications [Otuki, M. F., et al., 2011, Eur. J. Pharmacol. 672,175-179].
From a practical point of view, avocado oil unsaponifiables comprising non-acetylated PFA in a mixture with other extracted materials are useful in cosmetic and medicine.
Non acetylated fatty alcohols (such as structures C and F in FIG. 1) are naturally present in avocado seeds in minor amounts compared to the levels of the acetylated fatty alcohols. However, during saponification, the acetyl groups are essentially separated from the non-acetylated polyhydroxylated fatty alcohols. Thus, avocado oil non-saponifiables contains mostly acetyl-free PFA, which determine many of the biological properties of avocado unsaponifiables.
The known technique for obtaining unsaponifiables (as a part of the technological process for oil isolation and soap production) is extraction of avocado oil followed by alkaline saponification with potassium hydroxide or sodium hydroxide in alcoholic medium. The hydrolyzed compounds are extracted with a suitable organic solvent, for example petroleum ether, ethyl ether or any other suitable solvent that is immiscible with the aqueous-alcoholic solution. After several stages of washing and solvent evaporation, the extract of unsaponifiable may be used for formulations or may be additionally fractionated by different methods.
For example, U.S. Pat. No. 6,582,688 describes the use of molecular distillation for obtaining fractions of avocado unsaponifiables obtained from fruit pulp. The distillate is enriched with furan lipids or mixtures of furan lipids and polyhydroxylated fatty alcohols. In general, the material from avocado is obtained by controlled drying of the fruit pulp, extraction of the crude oil by cold pressing, preliminary molecular distillation of the oil, saponification of the distillate with ethanolic potassium hydroxide, extraction of the unsaponifiable material in a countercurrent column with an organic solvent, filtration, washing, desolvation and deodorization. The material from the avocado fruits obtained by the above described method is then resubjected to the step of molecular distillation.
Such methods are lengthy and labor intensive. An object is to provide easier methods of producing acetyl-free PFAs.